Optical coherence tomography (OCT) is a medical imaging technique that uses reflected light to produce an image. In OCT, light from a broadband light source is split by an optical fiber splitter with one fiber directing light to a sample path and the other fiber directing light to a reference path mirror. An end of the sample path is typically connected to a scanning device. The light reflected from the scanning device is recombined with the signal from the reference mirror to form interference fringes, which are transformed into a depth-resolved image. In swept-source OCT, the interference spectrum is recorded using a source with an adjustable optical frequency, in which the optical frequency is swept through a range of frequencies and the interfered light intensity is recorded as a function of time during the sweep.
Optical buffering, as used in swept-source OCT, is a method to copy, induce a relative delay (i.e., a buffer), and then recombine two or more optical signals in order to increase the effective imaging speed beyond that of the native imaging speed of the light source.
Traditionally, the buffering approach works by splitting the light source optical signal into multiple paths, delaying the signals with respect to each other, and then recombining the relatively delayed signals using an optical coupler into a common path for subsequent introduction into the OCT system. With this approach, imaging speed has been increased by as much as 16-fold over the native transmission speed of the light source.
The recombination of optically buffered signals using the typical 50/50 coupler, however, discards half of the optical power present in each light source sweep. This unfortunately leads to a reduction in overall system sensitivity. Moreover, the loss in power comprises image quality and has a negative impact on signal-to-noise.